1. Field of the Invention
This invention relates to liquid crystal displays (LCD), and more particularly, to an LCD having an electrostatic protection circuit.
2. Discussion of the Related Art
Generally, a liquid crystal display is a complex device that includes a liquid crystal panel, a light source, and driving circuitry.
The liquid crystal panel itself includes upper and lower transparent substrates and an interposed liquid crystal layer. On the upper transparent substrate are a system electrode, a black matrix layer, and a color filter layer. On the lower transparent substrate are a plurality of equally spaced gate lines that are arranged along one direction, and a plurality of equally spaced data lines that are arranged perpendicular to the gate lines. Thus there is a plurality of crossing points where the gate lines and the data lines cross.
Within an LCD panel Is an array of pixel regions defined by the spaces between the crossing gate and data lines. A pixel electrode and a thin film transistor (TFT) are arranged in each pixel region. The TFT gate electrodes connects to the gate lines, the TFT source electrodes connect to the data lines, and the TFT drain electrodes connect to the pixel electrodes. The gate and data lines are electrically connected to the driving circuitry. In operation, the thin film transistors are selectively turned on by gate signals applied to the gate lines. Furthermore, data signals are selectively applied to the data lines. The result is that the various TFTs apply signals to their electrodes so as to produce a desired image.
Often, static electricity is produced during the processing and/or testing of the LCD panels. When this static electricity is applied to the gate or data lines damage or destruction of the LCD panel can occur. One method of protecting arrays from static electricity uses common electrodes inserted between the driving circuit and the LCD array, with the common electrodes extending generally perpendicular to the gate lines and/or to the data lines. Then, electrostatic protecting circuits, such as varistors, diodes, zener diodes, unidirectional or bi-directional transient voltage suppressors, or bi-directional voltage triggered switches, are formed at the crossings of the gate and/or data lines and the common electrodes. By using such electrostatic protecting circuits the potential of the common electrode is applied to the gate and/or data lines by the electrostatic protecting circuit as required to protect the LCD panel. Accordingly, static electricity applied to the gate lines or to the data lines does little or no damage.
A related art LCD having an electrostatic protecting circuit will be described with reference to the schematic view of FIG. 1. In the related art LCD the electrostatic protecting circuits are arranged in parallel. A common electrode 4 extends between a driving circuit 1 and an LCD array 2 and perpendicular to the data or gate lines 3. An electrostatic protecting circuit 5 located near each crossing of the common electrode 4 and the lines 3. Further, as shown, each line 3 extends in a straight line between the driving circuit 1 and the LCD array 2.
While generally successful, the related art LCD shown in FIG. 1 has a problem. Since the electrostatic protecting circuits are located near the crossings of the common electrode 4 and the lines 3, it is very difficult to physically locate the electrostatic protecting circuits 5 if the lines 3 are closely spaced, as can happen in high resolution LCDs, or if the electrostatic protecting circuits are relatively large. Thus, new approaches to incorporating electrostatic protecting circuits would be beneficial.